In present day construction machines, such as a hydraulic excavator for example, the use of hydraulic cylinders to manipulate a work implement is quite common. A typical excavator includes a boom member that is pivotally connected to a frame of the machine, a secondary boom member, or stick, that is pivotally mounted to the boom, and a work implement that is pivotally mounted to a distal end of the stick. A hydraulic cylinder or a pair of hydraulic cylinders, depending on the size of the machine, are mounted between the frame and the boom member to move the boom member up and down with respect to the frame. At least one more hydraulic cylinder is positioned between the stick and the boom to move the stick with respect to the boom and the machine. Yet another hydraulic cylinder is positioned between the stick and the work implement to rotate the implement with respect to the stick. It is quite common for the hydraulic pressure requirements, especially in the boom and stick cylinders, to be quite high since it requires great force to manipulate the implement.
In many countries, especially those in Europe, there exist regulations, such as European Regulation ISO 8643, that require a load check valve to be connected to the pressurized end of the various cylinders to prevent the movement of the cylinders in the unlikely event that communication of the pressurized fluid to the cylinders is interrupted. Even more strict regulations require that this valve be connected directly to the cylinders without fluid conduits interposed therebetween. While this may seem to be a requirement that is relatively easy to satisfy, the movements and close proximity of the various components of an excavator make this an extremely difficult task, especially in the area of the boom. The reason for this stems from the positioning of both the lower portion of the boom and the hydraulic cylinder(s) on the forward portion of the frame. Since these members are massive and transmit great forces into the frame, there must be substantial reinforcement of the frame in this area. The reinforcement members must be in such close proximity to the boom and the stick cylinders, it is a very difficult to mount a valve directly on the boom cylinders without interfering with the frame or boom members.
The present invention is directed to overcoming one or more of the problems set forth above.